Photo-crosslinkable polyamide materials

ABSTRACT

Photo-crosslinkable materials comprising a linear polyamide and a 2-substituted anthraquinone as photo-crosslinking agent, the 2-substituted anthraquinone preferably being 2-acrylamidooanthraquinone, 2-acryloxyanthraquinone or 2-benzoylaminoanthraquinone.

This invention relates to materials based on linear polyamides and toarticles such as fibres and films produced from such materials, and inparticular to materials and articles which are photo-crosslinkable.

The normal effect of radiation on polyamides is to cause degradation bybreaking of the polymer chain. Although the use of a polymide inphoto-crosslinkable materials is known, the polymide itself takes littleor no part in the crosslinking, being only present as a support. In suchmaterials the photo-crosslinking is produced by a photopolymerisablemonomer containing, for example unsaturated groups as described in U.S.Pat. No. 4,144,073. An improvement can be effected by additionallyproviding unsaturated groups grafted onto the polymide backbone asdescribed in U.S. Pat. No. 4,421,840.

Surprisingly, it has now been found that photo-crosslinking ofpolyamides can be effected by using a suitable photo-crosslinking agentwithout the necessity of the unsaturated photo-polymerisable groupsbeing present.

According to one aspect of the present invention there is provided aphoto-crosslinkable material comprising a linear polymide and a2-substituted anthraquinone as photo-crosslinking agent.

According to a preferred aspect of the invention, the 2-substitutedanthraquinone has the formula ##STR1## where X is selected from a groupconsisting of NHC(O)CH═CH₂, OC(O)CH═CH₂, OC(O)C(CH₃)═CH₂ and NHC(O)C₆H₅.

The other positions on the anthraquinone ring may be optionallysubstituted.

Preferably the 2-substituted anthraquinone is 2-acrylamidoanthraquinone(X═NHC(O)CH═CH₂), or 2-acryloxyanthraquinone (X═OC(O)CH═CH₂), or2-benzoylaminoanthraquinone (X═NHC(O)C₆ H₅).

The photo-crosslinkable material may contain two or more of the2-substituted anthraquinones or a mixture of one or more of the2-substituted anthraquinones with one or more other photoinitiatormaterials.

Any polyamide may be used but poly(hexamethylene adipamide) (morecommonly known as nylon 6.6) or polycaprolactam (more commonly known asnylon 6) is preferred.

According to a further aspect of the invention there is provided asolvent--cast film or a melt spun fibre comprising a polyamide havingincorporated therein, or coated on the surface thereof, a 2-substitutedanthraquinone.

The 2-substituted anthraquinone may be incorporated into the polymerbefore or during the melt spinning or may be applied to the surface ofthe fibre as a spin finish or during the dyeing process.

Photo-crosslinking may be effected using radiation from sources havingemission maxima in the range 200 to 500 mm and especially in the range400 to 500 mm. Such sources may be actinic or super actinic fluorescenttubes, mercury vapour lamps and xenon lamps.

Whilst the 2-substituted anthraquinones are known generally, compoundscontaining a (meth)acryloxy group in the 2-position are novel.

Hence, according to a further aspect of the invention, there is provideda photoiniator compound having the formula ##STR2## where R is hydrogenor a methyl group.

The invention will be illustrated by the following examples.

EXAMPLE 1

Nylon 6.6 chips (2% by weight) were dissolved in trifluoroethanol and0.2% by weight 2-acrylamidoanthraquinone (AAAQ) added. A series of filmsamples was produced by spreading the resultant solution on glass platesand evaporating the solvent. Control samples not containing the AAAQwere also prepared.

The films were removed from the plates and irradiated for various timesusing a 400 watt mercury lamp.

The amount of gel formation, which is proportional to the degree ofcross-linking, was determined by dissolving a sample in a fixed volumeof formic acid, pouring the solution into a glass funnel containing aglass wool plug (the funnel and plug having been dried to constantweight) to filter out the undissolved gel, washing with a fixed volumeof formic acid and again drying to constant weight. The results areshown in Table 1.

EXAMPLE 2

Example 1 was repeated except that 2-acryloxyanthraquinone (AOAQ) and2-benzoylaminoanthraquinone (BOAAQ) were used. The results are alsoshown in Table 1.

                  TABLE 1    ______________________________________    Time      % Gel    (Minutes) Control  AAAQ       AOAQ  BOAAQ    ______________________________________    0         0        0          0     1.8    5         2.93     7.2        5.5    10        3.8      27.4       17.24    20                 45.0       41.14    30        12.44    59.4       53.53 42.2    ______________________________________

EXAMPLE 3

Samples of nylon 6.6, semi-dull, carpet yarn consisting of 68 filamentseach having an approximate decitex of 19 were boiled for 30 minutes inan 80/20 water/isopropyl alcohol solution containing 1% by weight AAAQand 5% by weight benzyl alcohol, the benzyl alcohol being present as aswelling agent for the nylon. Control samples were prepared in the sameway but without AAAQ present in the solution.

The dried samples were unravelled and laid on a flat surface beneath a400 watt mercury lamp for various periods, each sample being turned overhalf way through the period. The amount of gel formation was determinedin the same way as in Example 1. The results are shown in Table 2.

EXAMPLE 4

Example 3 was repeated using samples of nylon 6.6 film. The results arealso shown in Table 2.

                  TABLE 2    ______________________________________            % Gel    Time      Fibre               Film    (Minutes) Control  AAAQ       Control                                         AAAQ    ______________________________________     0        1.0      0          0      0    20        2.4      20.4       2.4    15.2    40        10.4     33.2       7.0    41.3    60        14.8     30.0       8.0    45.7    80        20.1     39.0    ______________________________________

EXAMPLE 5 SYNTHESIS OF 2-ACRYLOXYANTHRAQUINONE

2-hydroxyanthraquinone (2 g), water (125 ml), dioxane (25 ml) and KOH(20 g) were mixed together in an appropriate vessel in an ice bath. Adeep red colour was produced due to formation of a phenoxide salt of theanthraquinone. Acryloyl chloride was added dropwise until no furthercolour could be seen, whilst maintaining the temperature below 0.5° C.The residue was then filtered and washed with water followed byrecrystallisation from aqueous ethanol. The yield was approximately 60%.

We claim:
 1. A photo-crosslinkable material comprising a linearpolyamide selected from the group consisting of polyhexamethyleneadipamide and polycaprolactam and a 2-substituted anthraquinone as aphoto-crosslinking agent, said 2-substituted anthraquinone having theformula: ##STR3## where X is selected from a group consisting ofNHC(O)CH═CH₂, OC(O)CH═CH₂, OC(O)C(CH₃)═CH₂ and NHC(O)C₆ H₅.
 2. Asolvent-cast film comprising a polyamide having incorporated therein orcoated on the surface thereof a 2-substituted anthraquinone having theformula ##STR4## where X is selected from a group consisting ofNHC(O)CH═CH₂, OC(O)CH═CH₂, OC(O)C(CH₃)═CH₂ and NHC(O)C₆ H₅.
 3. Amelt-spun fibre comprising a polyamide having incorporated therein orcoated on the surface thereof, a 2-substituted anthraquinone having theformula ##STR5## where X is selected from a group consisting ofNHC(O)CH═CH₂, OC(O)CH═CH₂, OC(O)C(CH₃)═CH₂ and NHC(O)C₆ H₅.